U.S. patent number 7,746,982 [Application Number 12/211,721] was granted by the patent office on 2010-06-29 for rotary anode x-ray tube.
This patent grant is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Hitoshi Hattori, Yasutaka Ito, Hironori Nakamuta, Chiharu Tadokoro, Tetsuya Yonezawa, Yasuo Yoshii.
United States Patent |
7,746,982 |
Yoshii , et al. |
June 29, 2010 |
**Please see images for:
( Certificate of Correction ) ** |
Rotary anode X-ray tube
Abstract
In a rotary anode X-ray tube, a disc portion is fitted into a
rotary anode with a first gap therebetween and a fixed shaft is
fitted into a rotary shaft to support the anode with a second gap
therebetween. The disc portion and the fixed shaft are formed
integral with each other to have a hollow portion therein. A
cooling liquid is allowed to flow through the hollow portion. A
liquid metal is filled in the first and second gaps. Dynamic
pressure type bearings is formed in the second gap. A passage is
formed to directly communicate the first gap to the second gap,
whereby the liquid metal being directly supplied from the second
gap to the first gap. Thus, the liquid metal can be fed rapidly and
surely into the gap between the anode target and a cooling
vessel.
Inventors: |
Yoshii; Yasuo (Kawasaki,
JP), Tadokoro; Chiharu (Yokohama, JP), Ito;
Yasutaka (Kawasaki, JP), Hattori; Hitoshi
(Yokohama, JP), Nakamuta; Hironori (Otawara,
JP), Yonezawa; Tetsuya (Yaita, JP) |
Assignee: |
Kabushiki Kaisha Toshiba
(Tokyo, JP)
|
Family
ID: |
40030355 |
Appl.
No.: |
12/211,721 |
Filed: |
September 16, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090080616 A1 |
Mar 26, 2009 |
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Foreign Application Priority Data
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Sep 26, 2007 [JP] |
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2007-250220 |
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Current U.S.
Class: |
378/133; 378/144;
378/132 |
Current CPC
Class: |
H01J
35/104 (20190501); H01J 2235/106 (20130101) |
Current International
Class: |
H01J
35/10 (20060101); H01J 35/26 (20060101) |
Field of
Search: |
;378/132,133,144 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Glick; Edward J
Assistant Examiner: Artman; Thomas R
Attorney, Agent or Firm: Ohlandt, Greeley, Ruggiero &
Perle, L.L.P.
Claims
What is claimed is:
1. A rotary anode X-ray tube comprising: a rotary anode being
provided with a target on which an electron beam is irradiated to
generate X-rays, and having a first hollow portion; a rotary shaft
supporting the rotary anode and having a second hollow portion; a
disc portion fitted into the first hollow portion of the rotary
anode with a first gap therebetween and having a third hollow
portion; a fixed shaft being fitted into the rotary shaft with a
second gap therebetween, and having a fourth hollow portion
communicating with the third hollow portion of the disc portion; a
liquid metal filled in the first and second gaps; a dynamic
pressure bearing portion which is formed between an inner surface
of the second hollow portion of the rotary shaft and an outer
surface of the fixed shaft; and a passage which directly
communicate the first gap to the second gap to supply the liquid
metal to the first gap from the second gap, wherein the passage is
formed in the rotary shaft.
2. The rotary anode X-ray tube according to claim 1, wherein the
passage is set in pipes provided outside the rotary shaft.
3. The rotary anode X-ray tube according to claim 1, further
comprising other passages that directly communicate the first gap
to the second gap to supply the liquid metal to the first gap from
the second gap, wherein the other passages are formed in the rotary
shaft, and wherein the passage and the other passages have their
one ends opened into the first gap at regularly spaced intervals
around a tube axis of the X-ray tube and other ends opened into the
second gap at regularly spaced intervals around the tube axis of
the X-ray tube.
4. The rotary anode X-ray tube according to claim 1, wherein the
dynamic pressure bearing portion includes first and second dynamic
pressure bearings placed with a space therebetween along the fixed
shaft, the second gap includes a depressed region formed between
the first and second dynamic pressure type bearings, and the
passage is opened into the depressed region.
5. The rotary anode X-ray tube according to claim 1, wherein the
disc portion has an outer ring surface which is opposed to an inner
ring surface of the second hollow portion of the rotary shaft in
the peripheral portion of the fixed shaft, either of the inner ring
surface and the outer ring surface is formed with helical grooves
in the shape of a ring, and the passages are opened on the outside
of the helical grooves and communicate with the second gap.
6. The rotary anode X-ray tube according to claim 1, wherein the
fixed shaft has its one end fixed.
7. The rotary anode X-ray tube according to claim 1, wherein the
fixed shaft has its one end fixed.
8. A rotary anode X-ray tube comprising: a rotary anode provided
with a target on which an electron beam is irradiated to generate
X-rays, and having a first hollow portion; first and second rotary
shafts extended from the rotary anode in opposite directions along
its axis of rotation and having second hollow portions having inner
surfaces to support the rotary anode; a disc portion fitted into
the first hollow portion of the rotary anode with a first gap
therebetween and having a third hollow portion; first and second
fixed shafts having outer surfaces, the first and second fixed
shafts being extended from the disc portion in opposite directions
along the axis of rotation and being respectively fitted into the
first and second rotary shafts with a second gap therebetween and
having fourth hollow portions, respectively, and the third hollow
portion of the disc portion and the fourth hollow portion of the
first and second fixed shafts communicating with each other to
allow a cooling liquid to pass therethrough; a liquid metal filled
in the first and second gaps; first and second dynamic pressure
bearings which are formed between the inner surfaces of the second
hollow portions of the first and second rotary shafts and the outer
surfaces of the first and second fixed shaft, respectively; and
first and second passages which directly communicate the first gap
to the second gap to supply the liquid metal to the first gap from
the second gap, wherein the first and second passages are formed in
the first and second rotary shafts, respectively.
9. The rotary anode X-ray tube according to claim 8, wherein each
of the first and second fixed shafts is coupled to the disk portion
at its one end and fixed at its other end.
10. A rotary anode X-ray tube comprising: a rotary anode being
provided with a target on which an electron beam is irradiated to
generate X-rays, and having a first hollow portion; a rotary shaft
supporting the rotary anode and having a second hollow portion; a
disc portion fitted into the first hollow portion of the rotary
anode with a first gap therebetween and having a third hollow
portion; a fixed shaft being fitted into the rotary shaft with a
second gap therebetween, and having a fourth hollow portion
communicating with the third hollow portion of the disc portion; a
liquid metal filled in the first and second gaps; a dynamic
pressure bearing portion which is formed between an inner surface
of the second hollow portion of the rotary shaft and an outer
surface of the fixed shaft; and a passage which directly
communicate the first gap to the second gap to supply the liquid
metal to the first gap from the second gap, wherein the dynamic
pressure bearing portion includes first and second dynamic pressure
bearings placed with a space therebetween along the fixed shaft,
the second gap includes a depressed region formed between the first
and second dynamic pressure bearings, and the passage is opened
into the depressed region.
11. The rotary anode X-ray tube according to claim 10, wherein the
passage is formed in the rotary shaft.
12. The rotary anode X-ray tube according to claim 10, wherein the
passage is set in pipes provided outside the rotary shaft.
13. The rotary anode X-ray tube according to claim 10, further
comprising other passages that directly communicate the first gap
to the second gap to supply the liquid metal to the first gap from
the second gap, wherein the other passages are formed in the rotary
shaft, and wherein the passage and the other passages have their
one ends opened into the first gap at regularly spaced intervals
around a tube axis of the X-ray tube and other ends opened into the
second gap at regularly spaced intervals around the tube axis of
the X-ray tube.
14. The rotary anode X-ray tube according to claim 10, wherein the
disc portion has an outer ring surface which is opposed to an inner
ring surface of the second hollow portion of the rotary shaft in
the peripheral portion of the fixed shaft, either of the inner ring
surface and the outer ring surface is formed with helical grooves
in the shape of a ring, and the passages are opened on the outside
of the helical grooves and communicate with the second gap.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority
from prior Japanese Patent Application No. 2007-250220, filed Sep.
26, 2007, the entire contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a sliding bearing using a liquid lubricant
and a rotary anode X-ray tube using the sliding bearing.
2. Description of the Related Art
A rotary anode X-ray tube used in an imaging diagnostic system and
the like is used at a high temperature and in a vacuum, and
moreover the anode target is rotated at high speed. Such a rotary
anode X-ray tube is structured as disclosed in Japanese Patent
2960089 such that the rotation axis that supports the rotary anode
is supported by a sliding bearing which uses a liquid metal as a
lubricant. In order to further reduce the X-ray tube in size and
weight, it is required to cool the rotation target through a liquid
metal. For this reason, a proposal has been made for a structure
such that a gap is set between the back of the rotation target and
a fixed shaft and a liquid metal is injected into the gap as a heat
transfer fluid to thereby cool the rotation target.
With the rotary anode X-ray tube, when the X-ray tube apparatus is
operated, the anode target reaches a high temperature due to entry
of heat to it. That is, the anode target is irradiated with an
electron beam and consequently reaches a high temperature. In
particular, the electron bombardment surface (focal point) which is
struck by electrons reaches a high temperature. For this reason,
the anode target must be maintained at temperatures below the
melting point of its material.
From such a point of view, techniques to cool the anode target have
been developed. Among the techniques is one which uses a liquid
metal as a heat transfer fluid in the vicinity of the electron
bombardment surface and transfers the heat of the anode target to
cooling water within a cooling box, thereby cooling the anode
target.
However, the conventional rotary anode X-ray tube using the liquid
metal as a heat transfer fluid for cooling has the following
problem:
With the cooling mechanism which uses the liquid metal as a heat
transfer fluid for cooling, it is required to surely introduce the
liquid metal used as a lubricant into the gap between the cooling
box integral with the fixed shaft and the anode target. The amount
of the liquid metal to be filled in is limited so as not to cause
leakage from the seal portion when the rotating body is stopped.
When the rotating body starts rotating, the liquid lubricant is
pressed against the inner part of the rotating body due to
centrifugal force and then introduced from the fixed shaft into the
gap between the cooling box and the anode target.
However, the liquid metal needs to pass through the narrow gap in
the dynamic pressure type bearings; therefore, it takes long to
introduce the liquid metal into the gap between the cooling box and
the anode target.
BRIEF SUMMARY OF THE INVENTION
According to an aspect of the invention, there is provided a rotary
anode X-ray tube comprising:
a rotary anode being provided with a target on which an electron
beam is irradiated to generate X-rays, and having a first hollow
portion;
a rotary shaft supporting the rotary anode and having a second
hollow portion;
a disc portion fitted into the first hollow portion of the rotary
anode with a first gap therebetween and having a third hollow
portion;
a fixed shaft being fitted into the rotary shaft with a second gap
therebetween, and having a fourth hollow portion communicating with
the third hollow portion of the disc portion;
a liquid metal filled in the first and second gaps;
a dynamic pressure type bearing portion which is formed between an
inner surface of the second hollow portion of the rotary shaft and
an outer surface of the fixed shaft; and
a passage which directly communicate the first gap to the second
gap to supply the liquid metal to the first gap from the second
gap.
According to another aspect of the invention, there is provided a
rotary anode X-ray tube comprising:
a rotary anode provided with a target on which an electron beam is
irradiated to generate X-rays, and having a first hollow
portion;
first and second rotary shafts extended from the rotary anode in
opposite directions along its axis of rotation and having second
hollow portions having inner surfaces to support the rotary
anode;
a disc portion fitted into the first hollow portion of the rotary
anode with a first gap therebetween and having a third hollow
portion;
first and second fixed shafts having outer surfaces, the first and
second fixed shafts being extended from the disc portion in
opposite directions along the axis of rotation and being
respectively fitted into the first and second rotary shafts with a
second gap therebetween and having fourth hollow portions,
respectively, and the third hollow portion of the disc portion and
the fourth hollow portion of the first and second fixed shafts
communicating with each other to allow a cooling liquid to pass
therethrough;
a liquid metal filled in the first and second gaps;
first and second dynamic pressure type bearings which are formed
between the inner surfaces of the second hollow portions of the
first and second rotary shafts and the outer surfaces of the first
and second fixed shaft, respectively; and
first and second passages which directly communicate the first gap
to the second gap to supply the liquid metal to the first gap from
the second gap.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a schematic sectional view of a rotary anode X-ray tube
according to an embodiment of the present invention;
FIG. 2 is a schematic plan view illustrating a helical groove for
thrust bearing which are formed on the inner surface of the rotary
anode shown in FIG. 1;
FIG. 3 is a schematic sectional view of a rotary anode X-ray tube
according to another embodiment of the present invention; and
FIG. 4 is a schematic sectional view of a rotary anode X-ray tube
according to still another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
A rotary anode X-ray tube according to an embodiment of the present
invention will be described hereinafter with reference to the
accompanying drawings.
As shown in FIG. 1, the rotary anode X-ray tube is composed of a
cylinder-shaped fixed shaft 10 having its one end which is fixedly
supported, a cylinder-shaped body 60 of rotation which is rotatably
mounted to the fixed shaft 10, a hollow-disc-like rotary anode 50
which is fixed to one end of the rotary shaft 60 so as to rotate
together with it, a cathode 40 which is placed opposite a target 52
of the rotary anode 60 and emits an electron beam toward the anode
target 52, and a vacuum envelope (not shown) which houses these
components and has been evacuated to a sufficiently low
pressure.
The rotary shaft 60 is provided with a rotation producing unit 4
which is rotated together with the rotary shaft and made of a
conducting material, such as copper. The rotation producing unit 4
is opposed to a stator coil 2 which is placed outside the vacuum
envelope and adapted to produce a rotating magnetic field. When the
rotation producing unit 4 is subjected to the rotating magnetic
field from the stator coil 2, a magnetic field produced in the
rotation producing unit 4 and the rotating magnetic field repel
each other to generate a rotating force to rotate the rotary shaft
60.
The rotary anode X-ray tube and the stator coil 2 are accommodated
in a housing (not shown) to constitute an X-ray tube apparatus.
When an electron beam from the cathode 20 is directed focused onto
the rotating anode target 2, X-rays are generated from the anode
target and then directed to the outside through X-ray windows
formed in the vacuum envelope and the housing.
As shown in FIG. 1, the fixed shaft 10 is fitted into the rotary
shaft 60 so as to form gaps G1 to G5 therebetween. The gaps G1 to
G5 are filled with a liquid metal 30. To prevent leakage of the
liquid metal, the rotary shaft 60 is equipped at its open end with
a sealing member 61 to provide liquid-tight sealing between the
open end of the rotary shaft 60 and the base of the fixed shaft
10.
The fixed shaft 10 is constructed from a hollow cylinder-shaped
axial portion 14 and a hollow disc portion 16 fixed to the axial
portion. The axial portion 14 is formed on its circumference with a
pair of radial bearings 11 which are spaced apart from each other.
If the axial portion 14 can be supported by a single radial
bearing, only one radial bearing will suffice.
The radial bearings 11 are each formed with a helical groove, such
as a herringbone pattern. Between the radial bearings 11 is formed
a depressed region 15 to store the liquid metal 30. The gap G1
between the radial bearing 11 and the inner surface of the rotary
shaft 60 is set smaller than the gap G2 between the depressed
region 15 and the inner surface of the rotary shaft 60. When the
rotary shaft 60 is in rotation, the liquid metal 30 is supplied
from the gap G2 between the depressed region 15 and the inner
surface of the rotary shaft 60 to the bearing gap G1 through the
pumping action of the helical groove. Therefore, the dynamic
pressure in the radial direction increases through the liquid metal
supplied to the bearing gap G1 between the radial bearing 11 and
the inner surface of the rotary shaft 60. Thereby, the rotary shaft
is supported in the radial direction by the radial bearing produced
by the dynamic pressure.
Instead of forming a helical groove, such as a herringbone pattern,
on each of the radial bearings 11, the helical groove may be formed
in the inner surface portions of the rotary shaft 60 which are
opposed to the radial bearings. It is evident that only one of the
paired radial bearings 11 may be formed on the fixed shaft 10.
The hollow disc portion 16 is fitted into the hollow disc-shaped
rotary anode 50 to form the gaps G3, G4, and G5 between its
portions and the inner surface of the rotary anode. That is, the
outer circumferential surface of the disc 16 forms the gap G5. The
ring-like flat surface 16A of the disk portion 16 which is coupled
with the axial portion 14 forms the gap G4. The flat surface at the
top of the disc portion 16 forms the gap G4. As shown in FIG. 2, a
helical groove 18, such as a herringbone pattern, is formed in the
inside region of the ring-like flat surface 16A of the disc portion
16 to form a thrust bearing between the inside region of the flat
surface 16A and the inner surface of the rotary anode 50. As shown
in FIG. 2, the thrust bearing supports the rotary anode 50 along
the axial direction of the rotary shaft 60 through fluid dynamic
pressure of the liquid metal lubricant flowed in with the rotation
of the rotary anode. Likewise, a helical groove, such as a
herringbone pattern, may be formed on the flat disc surface at the
top of the disc portion 16 to provide another thrust bearing
between the disc surface and the inner surface of the rotary anode
50.
The rotary shaft 60 is formed with pipe passages 70 in order to
feed the liquid metal 30 into the gaps G3, G4 and G5 rapidly and
surely at the rotation of the rotary shaft. Each of the pipe
passages 70 is formed to extend obliquely and upward along a radial
line of the rotary shaft 60 and has its one end opened into the gap
G2 between the bearings 11 and its other end opened into the gap
G3. Moreover, in the gap G3, the other open end of the pipe passage
70 is formed, as shown in FIG. 2, outside the ring-like area in
which the helical groove 18 to produce fluid pressure is formed. As
shown in FIG. 2, the open ends of the pipe passages 70 in the gap
G3 are placed on radial lines of the rotary shaft 60 each of which
forms an equal angle with the adjacent one. Likewise, the open ends
of the pipe passages 70 in the gap G2 are placed on radial lines of
the rotary shaft 60 each of which forms an equal angle with the
adjacent one.
When the rotary shaft 60 is rotated, the liquid metal within the
gap G2 is pressed against the inner surface of the rotary shaft
through centrifugal force and part of it is fed into the pipe
passages 70. The liquid metal fed into the pipe passages 70 is
supplied to the gap G3. Here, the liquid metal within the pipe
passages 70 are smoothly supplied to the thrust bearing by the
pumping action of the bearing and then to the gaps G4 and G5 as
well.
The hollow portion of the hollow cylinder-shaped axis 14
communicates with the hollow portion of the disc 16. Both the
hollow portions are specified as a passage 20 for cooling water.
The axis 14 and the disc 16 constitute a cooling vessel 12. The
hollow portion of the axis 14 has its one end opened into the
outside. A tube for supplying cooling water (not shown) is inserted
into the open end of the axis 14. Cooling water is supplied through
this tube from the cooling water source of the cooling vessel 12 to
cool the disc 16. Cooling water may be directly supplied from the
cooling water source of the cooling vessel 12 to the passage 20
without inserting the cooling water supplying tube into the
passage.
When the X-ray tube apparatus is operated, the anode target 50
reaches a high temperature through entry of heat to it. That is,
the anode target 50 is irradiated with an electron beam and
consequently reaches a high temperature. In particular, the
electron bombardment surface (focal point) which is struck by
electrons reaches a high temperature. The heat is transferred from
the anode target 30 to the liquid metal 30 within the gaps G3, G4
and G5 and then to the disc 16 through the liquid metal. The heat
transferred to the disc 16 is then transferred to the cooling water
within the cooling vessel 12 and emitted to the outside of the
X-ray tube. With the rotation of the rotary shaft 60, the liquid
lubricant 30 is supplied through the pipe passages 70 to the gaps
G3, G4 and G5. Therefore, the heat transferred to the liquid metal
30 within the gaps G3, G4 and G5 are transferred to the disc 16 and
effectively led to the outside of the X-ray tube through the
cooling water. It is therefore possible to suppress the elevation
of temperature of the rotary anode 60 and prevent the anode target
50 from reaching its melting point.
FIG. 3 is a view, partially in section, of a rotary anode X-ray
tube according to another embodiment of the present invention. In
the X-ray tube shown in FIG. 1, the pipe passages 70 are formed in
the rotary shaft 60. In contrast, in the X-ray tube of FIG. 3,
pipes 71 are provided outside the rotary shaft 60. The pipes 71 may
communicate with openings 74 formed in the rotary shaft 60 and
openings 74 formed in the rotary anode 50. Openings 72 on the
rotary shaft side are formed in the gap G2 as in the structure
shown in FIG. 1, through which the liquid metal is supplied. In
addition, the openings 70 on the rotary anode side are formed to
communicate with the gap G3 and that are formed outside the area in
which the helical groove 18 is formed to increase fluid pressure.
When the rotary shaft 60 starts to rotate, therefore, the liquid
lubricant 30 stored in the gap G2 is pressed against the inside of
the rotary shaft due to centrifugal force and then supplied to the
gaps G3, G4 and G5 through the pipes 71.
Even with the X-ray tube equipped with the pipes 71 as shown in
FIG. 3, heat transferred from the rotary anode 50 to the liquid
metal 30 within the gaps G3, G4 and G5 is transferred to the disc
portion 16 and then effectively led to the outside of the X-ray
tube through cooling water. It is therefore possible to suppress
the elevation of temperature of the rotary anode 60 and prevent the
anode target 50 from reaching its melting point.
FIG. 4 is a view, partially in section, of a rotary anode X-ray
tube according to still another embodiment of the present
invention.
The X-ray tubes shown in FIGS. 1 and 3 adopt a cantilever structure
such that the fixed shaft 10 has its one end fixed and its other
end coupled to the disc portion 16 as a free end. This is not
restrictive. The X-ray tube of the invention may be formed into a
straddle-mounted structure such that, as shown in FIG. 4, first and
second fixed shafts 10 are coupled to both sides of the disc
portion 16 and extend in opposite directions along the central
axis. With this straddle-mounted structure, the disc portion 16 is
set between the first and second fixed shafts 10 as shown in FIG.
4. The hollow portions of the first and second fixed shafts 10
communicate with that of the disc portion 16 so that they
communicate with each other to form the passage 20 for cooling
water, thereby constituting a cooling structure to cool the rotary
anode 50.
The straddle-mounted structure with the first and second fixed
shafts 10 involves coupling to the rotary anode 50 of first and
second rotary shafts 60 into which the first and second fixed
shafts are fitted and which extend in opposite directions. The disc
portion 16 is fitted into the rotary anode 60, which is formed with
a helical groove 18 on its ring-like flat surface to provide thrust
bearing.
Each of the first and second fixed shafts 10 on opposite sides of
the disc portion 16 is provided with a bearing portion 11 to form a
radial bearing. A depressed region 15 is formed outside the bearing
11. The rotary anode 60 is provided with seal member 61 at their
both ends to prevent the liquid metal 30 from leaking to the
outside. The hollow portions of the first and second fixed shafts
10 and the disc communicate with one another to constitute a
cooling vessel 12 through which cooling liquid 20 flows.
Even with the X-ray tube of straddle-mounted structure shown in
FIG. 4, first and second pipe passages 70 are formed in the first
and second rotary shafts 70 to allow the gaps G2 and G3 to
communicate with each other. The liquid metal in the gap G2 is
supplied to the gap G3. Thus, the liquid metal is allowed to
circulate in the gaps G1, G2, G3, and G5.
The first and second pipe passages 70 are opened into the outside
of the area where the helical groove 18 is formed as shown in FIG.
2.
Even with the X-ray tube shown in FIG. 4, heat transferred from the
rotary anode 50 to the liquid metal 30 within the gaps G3 and G5 is
transferred to the disc portion 16 and then effectively led to the
outside of the X-ray tube through cooling water. It is therefore
possible to suppress the elevation of temperature of the rotary
anode 60 and prevent the anode target 50 from reaching its melting
point.
In the rotary anode X-ray tube of the invention, a liquid metal
required to cool the anode target can be supplied to the back of
the anode target directly (i.e., rapidly and surely) without
passing through narrow gaps in dynamic pressure type bearings;
therefore, a rotary anode X-ray tube can be provided which is
provided with sliding bearings using a liquid lubricant and which
is high in reliability.
Additional advantages and modifications will readily occur to those
skilled in the art. Therefore, the invention in its broader aspects
is not limited to the specific details and representative
embodiments shown and described herein. Accordingly, various
modifications may be made without departing from the spirit or
scope of the general inventive concept as defined by the appended
claims and their equivalents.
* * * * *